Semver notation isn't specifically used in package.json.

If it's followed (*1), it helps developers to understand what to expect from any particular update. Imagine you want to bump the version of a library, and you see that the difference is in the major part of the version (n in n.*.*). This can point out to potential repercussions of upgrading the package - according to SEMVER MAJOR version when you make incompatible API changes,.

*1 It's not always followed by developers. One prominent example is React Native. The developers have never released a Major version, and treat MINOR as MAJOR

I think the npm documentation explains it well: https://docs.npmjs.com/cli/v6/using-npm/semver#advanced-range-syntax

Since there is a lot going on, perhaps a brief explanation of the two most common:

The caret modifier (^) will automatically go the highest minor and patch version, unless the major version is 0. In this case, will only update the patch version.

The tilde modifier (~) will only go to the highest patch version. So ~ and ^ are equal when the major version is 0.

I got this from node js documentation. There is a pretty well explanation for question.

https://nodejs.dev/learn/the-package-lock-json-file

In package.json you can set which versions you want to upgrade to (patch or minor), using the semver notation, for example:

• if you write ~0.13.0, you want to only update patch releases: 0.13.1 is ok, but 0.14.0 is not.
• if you write ^0.13.0, you want to get updates that do not change the leftmost non-zero number: 0.13.1, 0.13.2 and so on.
• If you write ^1.13.0, you will get patch and minor releases: 1.13.1, 1.14.0 and so on up to 2.0.0 but not 2.0.0.
• if you write 0.13.0, that is the exact version that will be used, always